(1) Field of the Invention
This invention relates to apparatus for conducting hydrodynamic tests on a model, and more particularly relates to an inflatable bag for sealing the gap between the underside of a model and the bottom of a tank in which the model is mounted to improve the accuracy of the data obtained while the model is undergoing hydrodynamic tests, and to a method of using the bag to obtain such data.
(2) Description of the Prior Art
The continuing development of offshore structures has been preceeded by the construction and testing of models of such structures in hydrodynamic test facilities, such as wave tanks. Such testing has been conducted to obtain data which may be used in the design of the full scale structures and which takes into account the loads applied by environmental forces, such as wind, waves, currents, and moving sheets of ice. Some of the structures which have undergone such tests are the so-called gravity-based types which are floatable to designated sites and there submerged to rest on the sea floor. When in place, the weight of such gravity-based structures is capable of resisting the expected environmental loads through the friction of the contact surfaces of the base and the foundation on which it is resting.
To improve the accuracy and reliability of the data obtained from tests of models of gravity-based exploratory structures, such models have been mounted in wave tanks and supported therein by load cells with the flat underside of the model spaced above the tank bottom. Such a set-up eliminated the errors that would otherwise be introduced into the data obtained from the output of the load cells due to frictional contact between the model and the tank bottom during tests. However, while the aforementioned set-up reduced errors, errors were sometimes introduced as a result of the hydrodynamic forces acting in the gap between the underside of the model and the bottom of the tank. Consequently, a need has existed for a structure or device, which could be used to prevent the aforementioned hydrodynamic forces from acting on the model in the gap and which could be used to obtain data that could be integrated with that obtained from the load cells so as to render the load cell data more accurate and reliable.